It is a simple opening, but devastatingly poignant in context: teenage girls talking about getting ready to go to a concert. “I wanted something off the shoulder,” says one. “Like girly, but not girly. Like Ariana Grande.” It is poignant because, even now, these teenagers are able to recapture that sense of anticipation. It is devastating because you know what is coming next.

Grande performed her last number and walked off stage shortly before 10.30pm, perplexing a lot of her young fans. “It was the Dangerous Woman tour and she hadn’t sung Dangerous Woman,” says Acacia Seward, 12. By the time Grande came out and did the song as an encore, a good proportion of the audience were already making their way through the foyer.

The device went off at 10.31pm, while the bomber stood among parents waiting to collect their children. The moment of the explosion is recalled by survivors in a litany of horrifying details. People were lifted off their feet. The doors blew open, then shut themselves. The foyer was filled with a bright white light – “Like snow coming towards you” – and then darkness as it was suffused with smoke. Nuts and bolts from the device ricocheted, making a sound like machine-gun fire. For some victims, the immediate aftermath was eerily silent: their eardrums had been perforated. There was blood everywhere and people struggled to grasp the extent of their injuries. “I saw my legs were on fire and then I was unconscious,” says Eve Senior, 15.

A countdown clock (reminiscent of the one Grande employed as her big entrance approached) winds back to the moment of the explosion for another perspective. Phone footage recorded the panic inside the auditorium, where there was a stampede of people trying to get out – running towards the carnage by the exits. In all the confusion, rumours about gunmen spread.

Winding back again, the documentary adopts the point of view of the emergency services. Four transport police were on duty at Victoria railway station, connected to the arena by a footbridge. They ran toward the scene, in the opposite direction of the fleeing crowds. “If you can imagine hell,” says PC Steve Corke, “times it by a million”.

Because of the possibility of secondary devices – there were abandoned bags everywhere – arriving ambulance crews were kept back, even as members of the public ran toward the danger to help. With no proper medical equipment on the scene, the flow of blood was stemmed with Grande T-shirts. Victims had to be ferried to the train station to get medical attention. The safety protocols in place were much criticised after the fact, but the documentary obliges you to experience the confusion, the agonising and frustration over decisions taken, for better or worse, on the night.

The other main strand of the film concerns the 23rd fatality: 22-year-old Salman Abedi, sliced in two by his own bomb. Born and bred in Manchester, Abedi had returned to the city four days before on a flight from Libya. His parents, who fled Libya during the Gaddafi regime, had recently gone back there to live. A difficult and sometimes violent student, Abedi was fighting on the front line in Libya’s civil war by the age of 17. In the months before the attack, he was living alone in the family home in Manchester. His exact motivations remain opaque, but police say he would have been incapable of making the bomb he used without close guidance. Abedi does not qualify as a victim alongside those he killed, injured and traumatised that night, but he is bound up in the tragedy all the same.

Manchester: The Night of the Bomb provides a gruelling evocation of that tragedy. Some of it – such as the recorded announcement still blaring out the words “Attention: due to an incident, it is necessary to evacuate the area” long after the building had been emptied of anyone who could walk – is positively haunting. But it is also, in the end, inspiring, thanks to the determination of those present to tell their stories.